How Many Neon Tetras in a 10 Gallon Tank?

A 10-gallon tank can house five to six neon tetras. Some people may try to add more Tetras because they’re small fish. However, more than six neon tetras will overcrowd the small tank.

Neon tetras are small but active fish, so they need space to swim around freely. What’s more, they’re shoaling fish, so they’re at their healthiest when living in schools of at least six neon tetras.

In this article, we’ll explain why you need a specific number of neon tetras in a 10-gallon tank and what can happen if the tank is overcrowded.

How Many Neon Tetras in a 10 Gallon Tank?

The number of fish you can keep in a tank typically depends on fish size and tank size.

Except for some that grow to be around 1.75 inches long, most neon tetras grow to be around 1.5 inches long. So, you can raise about six neon tetras in a 10-gallon tank.

In a community tank, however, you’ll have to take into account the size of the other fish.

Another factor to consider is the social temperament of neon tetras. These fish need to be in groups of their own kind to thrive.

Otherwise, they may experience stress, depression, and loneliness. This can lead to appetite loss, discoloration, a weakened immune system, and, in worst-case scenarios, loss of life.

So you should have at least four neon tetras in one tank, but preferably six.

To ensure that you have the correct number of fish in your tank, some calculations can help you determine the stocking number for any given tank size.

Neon Tetra

How to Calculate the Number of Neon Tetras for a Tank

For fish under three inches long, one gallon of water for every inch of fish is a good rule of thumb. So, dividing the tank’s size by the average length of a neon tetra gives us the number of fish that tank can hold.

To be safe, let’s assume that all neon tetras grow to be 1.75 inches long. So, 10 gallons divided by 1.75 inches equals 5.71. If we round it up, we get six, which is the maximum number of neon tetras a 10-gallon tank can house.

If you want to add tank mates to your neon tetras, you can use the same calculation to determine how many you can add to the tank without drastically reducing the number of tetras.

So, what matters is that you use a liberal estimate of fish size rather than an exact estimate. This reduces the possibility of having a tank that is too small for your tetras school.

What Happens If You Put Neon Tetras in a Small Tank?

Overcrowding your tank with neon tetras can have several negative consequences for both the fish and you. These consequences include stress, stunted growth, excess waste, diseases, infections, and aggression.


Bullies, a lack of resources, and dirty water are more likely in an overcrowded tank. In addition, neon tetras are active swimmers, so the cramped space hinders them from swimming freely.

Despite their adaptability, such conditions can stress neon tetras out.

As a result, a stressed-out neon tetra may lose its appetite and develop a weakened immune system, exposing it to a variety of health problems.

Stunted Growth

Stunted growth is one of the consequences of stress and poor living conditions in fish. In such circumstances, the fish’s body diverts its nutritional resources to survival rather than growth.

In addition, several studies have linked stunted growth to the hormones fish release when stressed. Stressed fish can produce growth-inhibiting hormones, which can stunt the growth of nearby fish.

In the wild, fish can move away from the source of stress. However, in a confined tank, the fish will remain stressed until the tank owner resolves the issue. Meanwhile, the stressed fish continues to produce growth-inhibiting hormones, possibly affecting other fish.

Excess Waste

In theory, a 10-gallon tank is easy to clean. However, water parameters tend to be volatile in small enclosures. So, if you overstock your tank, it’ll get dirty faster.

Your neon tetras generate waste that degrades into ammonia and nitrites. This process reduces the amount of oxygen in the tank, which your fish and plants require to survive.

As a result, the tank will require more frequent cleaning to keep the tank inhabitants healthy.

Diseases and Infections

Stress and poor water quality can cause a variety of diseases and infections in neon tetras.

The following are some of the most common diseases that neon tetras may suffer from as a result of overcrowding:

  • Dropsy
  • Neon Tetra Disease
  • Bacterial Gill Disease
  • Trichodina infection


In some cases, overcrowded neon tetras may start displaying aggressive behavior. The lack of space can make it difficult for the fish to participate in shoaling behavior. As a result, they may become stressed, which can lead to aggression.

What’s more, despite being shoaling fish, neon tetras prefer to have enough space to swim freely or hide. neon tetras may become agitated if they don’t have enough space to do so, which can result in aggression.

Limited Chance of Creating a Community Tank

To meet all of the requirements for neon tetras in a 10-gallon tank, there isn’t much room for another fish.

Guppies, for example, are a good tank mate for neon tetras, which can grow to be up to 2.4 inches long. If you add two guppies to a 10-gallon tank, your neon tetras will only have about five gallons, which is only enough space for three tetras.

So, creating a healthy, happy community would be impossible without overcrowding the tank.

Have Another Tank Size You’re Looking At?

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In Conclusion

Following the one-gallon per one-inch rule, you can raise around six neon tetras in a 10-gallon tank.

Just keep in mind that a 10-gallon tank is the minimum size for a school of neon tetras. So, if you want your neon tetras to thrive and participate in schooling behavior, you should put them in a larger tank.

Neon tetras need their space to swim around and group together. Giving them these conditions can help them live healthier lives and lower their risk of suffering from health problems.